KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility at NASA?s Kennedy Space Center, technicians check out the base of the Manipulator Positioning Mechanism (MPM) installed on the starboard side of Atlantis? payload bay. The MPM will hold the 50-foot-long Orbiter Boom Sensor System (OBSS) that will attach to the Remote Manipulator System, or Shuttle robotic arm. The OBSS is one of the new safety measures for Return to Flight, equipping the orbiter with cameras and laser systems to inspect the Shuttle's Thermal Protection System while in space. Atlantis is scheduled to fly on Return to Flight mission STS-121, which has a launch window of July 12 to July 31, 2005.